The co-production of propylene oxide and styrene monomer, also known as the ‘POSM’ process, involves the oxidation of ethyl benzene to form ethyl benzene hydroperoxide, the catalytic reaction of the hydroperoxide with propylene to form propylene oxide and 1-phenyl ethanol, and the dehydration of the 1-phenyl ethanol to produce styrene monomer. In the POSM process, various distillation steps are employed in order to separate unreacted reagents, as well as various product streams, and one or more caustic treatment steps may be employed in order to reduce the acidic characteristics of various streams. In the process, a heavy residue stream containing relatively high levels of sodium compounds is formed. Without further treatment, the heavy residue stream is a low value product stream that may be useful only as a low grade fuel.
The low value product stream is conventionally treated with aqueous acid to form a mixture, and then phase separation of the resulting mixture provides an aqueous phase containing most of the sodium previously associated with the low value stream, and an organic phase having a reduced sodium content which can be used as higher grade fuel.
In conventional phase separation processes, it is often found that large volumes of a rag layer tend to form in the separator vessels. The rag layer is an emulsion of water in the heavy organic layer that does not separate into either an organic or an aqueous phase. The rag layer prevents complete separation of the aqueous and organic phases, and reduces the efficiency of the separation process.
Accordingly, an ongoing need exists for systems and methods for upgrading low value heavy residue(s) produced in the POSM process.